---
type: Monitoring Guide
title: "How to Monitor Fan Speed (RPM) via SNMP"
description: "Read ENTITY-SENSOR-MIB rpm sensors, detect a stalled or failing fan against a floor, and alert on any single failure in an N+1 group."
resource: "https://snmp-monitoring.info/monitoring/hardware/fan-speed/"
tags: [monitoring]
timestamp: 2026-07-11T00:00:00Z
---

# How to Monitor Fan Speed (RPM) via SNMP

Read ENTITY-SENSOR-MIB rpm sensors, detect a stalled or failing fan against a floor, and alert on any single failure in an N+1 group.

## Related concepts

- Up: [SNMP Hardware Monitoring: Temperature, Fans, Power & RAID](/monitoring/hardware/index.md)

## Frequently asked questions

### What OID is fan speed in SNMP?

The portable one is entPhySensorValue (1.3.6.1.2.1.99.1.1.1.4) from the ENTITY-SENSOR-MIB, for any sensor whose entPhySensorType is rpm. Labelled per-fan data with a health status usually comes from a vendor enterprise MIB under 1.3.6.1.4.1; the exact index is device-specific.

### How do I detect a failed fan?

Alert on 0 RPM for a fan that should be spinning — on a non-variable fan that's an unambiguous failure — and also on a drop below the fan's normal RPM floor to catch one that's failing but not yet dead. Watch each fan individually so a single failure in an N+1 group is visible.

### Can SNMP read server fan RPM?

Yes. Fans appear in the ENTITY-SENSOR-MIB typed as rpm, and server platforms expose them through their enterprise MIBs too. Reading RPM directly is the earliest warning of a cooling problem, well ahead of any thermal alarm.

### Why is my fan running at max RPM?

Sustained maximum RPM across the fans usually means the hardware is hot and the cooling system is ramping up to compensate — the fans are working, not failing. Treat it as a thermal signal and investigate temperature and airflow rather than the fan itself.

## Source

Concept generated from https://snmp-monitoring.info/monitoring/hardware/fan-speed/ — the SNMP Monitoring vendor-neutral knowledge base. Content is limited to what that page states (no external claims added here).